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Application Note 020 Converting a 1 Form A / 1 Form B Relay into a 1 Form C Relay

Figure 1: 1 Form A / 1 Form B Connection

Application Note 020 Converting a 1 Form A / 1 Form B Relay into a 1 Form C Relay
Figure 1: 1 Form A / 1 Form B Connection
AppNote 020
value of 400 does not take into account any temperature or tolerance variations. The main point to keep in consideration when connecting pins 2 & 3 is that the input driver circuitry experiences two forward LED voltage drops instead of just one.
Conclusion The Solid State Optronics 1 Form A / 1 Form B relays can be configured to create a 1 Form C relay by connecting pins 2 & 3. By connecting the two input LEDs in series, a single input can thus be used to switch the Form A and Form B relays. However, when connecting the relay in 1 Form C fashion, two LED forward voltage drops are encountered instead of one. These voltage drops must be considered when designing the input circuitry. Finally, at higher input currents, "break before make" functionality is inherently exhibited.
Figure 2: 1 Form C Connection
Break Before Make Functionality Inherent in an electromechanical 1 Form C relay is "break before make" functionality. The AD4C113 solid state relay, when wired in the 1 Form C configuration, likewise exhibits the "break before make" contact properties. Although both LEDs are operated simultaneously via the same input signal, the switching speeds of the Form B and Form A portions of the relay differ. The Turn Off time of the Form B portion is much faster than the Turn On time of the Form A relay. This difference in switching speeds creates the "break before make" switch characteristics. Higher input control currents can help maximize the effectiveness of "break before make" functionality.
AppNote 020